Array.prototype.my_includes=function(value,start=0){
    for(let i=start;i<this.length;i++){
        if(this[i]==value){
            return true//判断是否包含指定值
        }
    }
    return false
}
let arr=[1,2,4,5,7,8]
let result = arr.my_includes(2,3)
console.log(result)